<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style>
blockquote::before { content: attr(id); }
</style>
<style>
@supports (display: block) {
  #case1 {
    background-image: url(resources/case1.bmp);
  }
}
</style>
<style>
@supports (display: nonexist) {
  #case2 {
    background-image: url(resources/case2.bmp);
  }
}
</style>
</head>
<body>
<blockquote id="case1"></blockquote>
<blockquote id="case2"></blockquote>
</body>
</html>
